Air, gas, or like fluid compressor



Feb. 22, 1955 T. M. s. PIENAAR AIR, GAS 0R LIKE FLUID COMPRESSOR 2 Sheets-Sheet 1 Filed July 18, 1951 INVENTOR. mm 05 MOrf/vinus 5/1 .QIJLAIJ man P/enaar Iii, MM M Fig. 2

Feb. 22, 1955 T. M. s. PIENAAR 2,702,664

AIR, GAS OR LIKE FLUID COMPRESSOR Filed July 18, 1951 2 Sheets-Sheet 2 27 I2 I4 77 B f (7 l N L 1 I L [T A LA f 9 '5 21 Fig. 3 /0 -14- p-D Y (g 44$) m L l\ T'\ 1 C CJ Fig. 3 Confinuea Fly. 4

INVENTOR. /761/17/5 Marff nus Plenum B u/JKQJ Mu PM United States Patent AIR, GAS, OR LIKE FLUID COMPRESSOR Theunis Marthinus Snyman Pienaar, Mayville, Pretoria, Transvaal, Union of South Africa Application July 18, 1951, Serial No. 237,390

Claims priority, application Union of South Africa July 31, 1950 Claims. (Cl. 230-108) This invention relates to an improved compressor for compressing air, gas and other gaseous fluids and is particularly, but not exclusively, applicable for compressing air for driving rock drills, jack hammers and like pneumatic tools or machines. For convenience only, reference will hereinafter be made to air only as the fluid to be compressed and must be considered to include gas or other gaseous fluids.

An object of the present invention is to provide an air or like gaseous fluid compressor wherein pistons and like reciprocating parts, which are subject to excessive wear and which require continual maintenance, are eliminated while a greater efliciency is obtained.

According to the present invention the air compressor consists of a driven liquid pump, a pressure tank and a liquid jet injector with which an air inlet is associated all being connected together in that order to form a closed circuit through which a liquid is circulated, said liquid, during its passage through the jet injector, taking up air which with the liquid is forced into the tank by the pump and in which tank the liquid and air separate, the liquid collecting in the bottom of the tank under the air which is compressed in the top part of the tank while said liquid is forced by the pressure of the air into an end pipe leading to the liquid jet injector.

The liquid in the tank is forced through a nozzle to produce a jet which is directed into a Venturi tube by the pressure under which the liquid is contained in the pressure tank. The liquid jet evacuates the air from the space between the Venturi tube and the nozzle and such evacuated air is drawn into the Venturi tube by the jet and is pumped with the liquid into the pressure tank in which the air separates from the liquid.

Any suitable pump of the positive type, capable of pumping the air and liquid separately may be employed but should preferably be of the rotary kind capable of building up pressure to force the liquid through the nozzle of the jet injector. By way of example such pump may consist of a gear pump, multi-stage centrifugal pump, turbine pump or the like.

The nozzle is preferably of a kind having an axial aperture which is flared at the rear end whereas the Venturi tube provides a restriction in its front part and a constant bore intermediate part extending between said restriction and a rearwardly diverging conically shaped passage. The air inlet or suction pipe communicates with the space between the nozzle and Venturi tube so that the liquid jet may evacuate the air from such space.

The rear end of the Venturi tube of the jet arrangement is connected to the suction connection of the pump while the delivery connection of said pump is connected to the pressure tank by means of a pipe at a position above the liquid level. The liquid is drawn from the tank at the bottom of the latter while the compressed air is drawn off at the top end of the tank at which position the usual gauges and safety valve are also mounted.

Any suitable liquid with no, or very little frothing qualities, e. g. water, may be employed in the apparatus, while a plurality of jets, arranged in parallel with one another, may be used instead of a single jet. If desired two or more pumps may be employed. The pump or pumps is or are driven by any suitable motor or engine.

In order that the present invention may be more clearly understood reference is now made to the accompanying drawings in which like reference numerals refer to like parts throughout the several views. Further fea- "ice tures of the invention will be apparent from the following description.

In the drawings:

Figure l is a sectional elevation of an air compressor according to the present invention particularly suitable as a small capacity portable or mobile compressor;

Figure 2 is a diagrammatic representation of a compressor according to the present invention, incorporating a plurality of jet injectors and suitable for a large capacity plant;

Figure 3 and Figure 3 continued are longitudinal crosssections of the nozzle and venturi tubes for use on the apparatus shown in Figure 1;

Figures 4, 5, 6 and 7 are outlines of four modified forms of venturi tubes for use on compressors according to the present invention; and

Figure 8 is a cross-section of a simple form of construction of a venturi tube.

Referring to Figure 1 of the drawings the pressure tank is denoted by reference numeral 1 and the pump by numeral 2. The delivery end 5 of the pump 2 is provided with a tube 3 which extends into the tank 1 and terminates at a position above the liquid level 4 in the tank 1. The intake end 6 of the pump 2 is connected to a tube 7 mounted on the outside of the tank 1 and has connected thereto end pipe 8 extending into the tank 1 to terminate at a position close to the tank bottom and well below the liquid level 4.

The tube 7 is provided with a branch tube connecting unit 9 intermediately of its ends whereby the air intake tube 10 is connected to said tube 7. The tube 7 forms the housing or mounting for the discharge nozzle 11 and venturi tube 14 as is clearly shown in Figures 3 and 3 continued.

The discharge nozzle 11 presenting preferably a slightly flared discharge end 12, is adjustably fixed in the front part or wall 13 provided in the connecting unit 9, while the venturi tube 14 having a restricted throat is secured concentrically with the nozzle 11 in the rear end of said unit 9 in spaced linear coacting relationship to the nozzle 11. The adjustment of the nozzle 11 is in respect of its spacing from the front end of the venturi tube 14 and for this purpose is preferably screw-threaded and engageable in a correspondingly screw-threaded hole in the part 13 of the unit 9.

The pump 2, which may consist of a gear pump, turbine pump or any other suitable, but preferably rotary pump capable of building up a pressure, is driven by electric motor 15 while a pressure trip switch 16 is provided for stopping the motor when a desired maximum pressure has been developed in the tank 1. A filter 17, pressure gauge 18, controlled air outlet 19 and safety valve 20 are all mounted on the tank 1 as is common practice on air compressors.

In operation the air pressure on the liquid in the tank 1 forces the liquid through the nozzle 11 to create the jet for drawing in air into the venturi tube 14 while the liquid and air, discharging from said tube 14, are forced by the pump 2 into the tank 1 where air separates from the liquid, the latter remaining in the bottom of the tank where it is available for recirculation. For better separation of the air from the liquid the pipe 3 discharges into a cup-like element or baflie 21, rigidly mounted in spaced relationship across the discharge end of said tube 3.

The space around the nozzle 11 and the front end of the venturi tube 14 communicates direct with the atmosphere through tube 10. The lower end of said tube 10 is preferably contained in a cup shaped container 23 which receives liquid leaking past the pump bearing glands in order to be drawn back into the circuit. Said container 23 is connected to the pump 2 by a tube 24 for leading the leakage liquid to the container 23. A unidirectional valve 25 is provided on the tube 10 to prevent excessive fluid discharge when the apparatus is stopped and a back pressure becomes effective through the pump 2.

The adjustment of the nozzle 11 during operation of the apparatus is conveniently effected by a rotatable and axially slidable member 26 which extends outwardly of the tube 7 through a gland or the like. The inner end of said member 26 may be brought in engagement with notches or slits 27 in the nozzle whereby thelatter may be screwed towards or away from the venturi tube for setting it in a position for maximum efliciency of operation.

In, Figure 1 the tank 1 is horizontally disposed but this location is for convenience only and may, if desired, be mounted vertically.

Referring to Figure 2 an arrangement for a large capacity compressor is diagrammatically illustrated. In this arrangement the tank 1 is vertically disposed and is providedlwith a cooler 28 through, which the liquid is circulate'dby-pump 29. The tank l may be provided internally with, baflle plates 30 to facilitate the separation of the air and liquid and also to prevent air turbulances from carrying liquid to the air discharge in the top of the tank.

In the event of one nozzle beinginsuflicient to supply a required volumeof .air a plurality of nozzles, each having a venturi tube, may be'provided and associated with two manifolds 31.and 32. Each nozzle 11 and its co-acting venturi tube 14 is housed within a housing tube 7a provided with an air inlet 33. Said tubes 7a are preferably mounted vertically with the nozzles 11 in their upper regions while the upper manifold 31 is connected by tube 8a to the lower region of the tank 1. The lower manifold is connected to pump 2 by tube 34 and the tube connection 34 between the lower manifold 32 and pump 2 may be in the form of a venturi tube for more eflicient operation of the apparatus.

For large compressors, where it is not practicable to stop the motor or engine when the desired maximum pressure is obtained, an automatic cutout or by pass valve arrangement is provided comprising a tube 35, having a unidirectional valve 36, connecting the tank 1 with the lower manifold 32 so that when the maximum pressure is reached, the valve 36 opens and the pressure on both sides of the pump is thus equalized and as a result of which the pump 2 may operate under no-load conditions. The back pressure in the venturi tubes 14 stops the action of the nozzles while unidirectional valves 25, provided on the air intakes 33, prevent the escape of air through the air inlets. The valve 36 may be loaded by spring 39 or other means, preferably adjustable, and may be of any known construction. The tube 35 and valve 36 must be sufficiently large to provide for sufiicient air to pass'in order to stop the flow of the fluid through the nozzles.

The air may be introduced into the air intakes under increased pressure and for this purpose a supercharger (not shown) of known construction may be provided.

In Figure 2 the plurality of nozzle housing tubes 7a are arranged parallel and adjacent one another in a plane, but any other parallel arrangement of such tubes, such as for instance in a circle, may be employed if desired. Such tubes may bearranged vertically or horizontally.

Various kinds of venturi tubes may be employedwhich vary as regards their lengths and shapes according to varying operating conditions. The arrangement shown in Figures 3 and 3 continued have provided satisfactory results on small compressors. In this arrangement the section A of the venturi tube 14 has a straight central part. The next section B provides a straight and constant bore passage of the maximum venturi rear end diameter, and the third section C provides a restricted throat of a reduced diameter and having a conical reduction part c in its front end, while thetail section D is of outwardly diverging or flared shape having a minimum aperture equal to the diameter of the passage in the adjacent section.

Figures 4, 5, 6 and 7 illustrate other arrangements which have proved satisfactory.

However, good results have been obtained with a venturi tube provided at its front end with a straight parallel section and diverging rearwardly either along gradual curves or in stepped formation. In Figure 8 a cheap construction of stepped formation is shown constructed from a plurality of reduction sockets 37 and short pipe lengths 38. The largest pipe length 38 extends into a pressure box 40 from whence the fluid is pumped by pump 2 to the tank 1.

Where limited space prevents the use of a venturi tube having a straight axis, the tube may be compacted by constructing it in the form of one or more helical convolutions.

Compressors constructed according to the present invention may be driven by engines or electric motors and, as they are no load starting units, no special starting provisions need be made.

What I claim is:

1. An air compressor comprising a fluid pump, a single pressure tank for holding liquid and air under pressure, a tube connecting the output end of the fluid pump to the pressure tank; an intake pipe connected to the intake end of said pump and which pipe is provided with an end pipe extending into the tank and terminating below the level of the liquid in said tank, a flared discharge nozzle concentrically secured within the intake pipe, said discharge nozzle comprising a liquid jet forming nozzle, and a venturi tube arranged in line with said nozzle having a coacting restricting throat, an air inlet communicating with the intake pipe at a position between the nozzle and the venturi tube, said liquid jet entrains air from said air inlet when the liquid is forced by air pressure from the pressure tank through the nozzle, such air entrained liquid being directed into the intake end of said pump which in turn forces such air entrained liquid into the pressure tank against the pressure existing in such tank and in which tank the liquid separates from and collects under the air while the liquid is forced by the pressure of the air into the end pipe.

air compressor comprising a fluid pump, a pressure tank for holding liquid and air under pressure, a delivery tube connected by one end to the output end of the fluid pump and having the opposite end in fluid communication with the pressure tank at a position above the level of the liquid in said pressure tank, an intake pipe connected by one end to the intake end of said pump and provided at the opposite end with an end pipe dipping below the level of the liquid in said tank, a flared discharge nozzle concentrically secured within the intake pipe, said discharge nozzle comprising a liquid jet forming nozzle and a venturi tube arranged in line with said nozzle having a coacting restricted throat followed in spaced relationship by a coacting restricted throat section, said venturi tube and said restricted throat section being in axial alignment with one another, and an air inlet pipe having a unidirectional valve therein which pipe communicates with the intake pipe at a position between the jet forming nozzle and the venturi tube, said discharge nozzle having a flared opening facing the direction 'of the end pipe, said liquid jet ejected from said discharge nozzle by the air pressure in the tank entrains air from said inlet pipe and such air entrained liquid is directed into the intake end of said pump which in turn forces such air entrained liquid into the pressure tank against the pressure existing in the tank where the liquid separates and collects under the air while the liquid is forced by the pressure of the air into the end pipe.

3. An air compressor as claimed in claim 2 wherein the said flared discharge nozzle is axially adjustable to control the position of said nozzle with respect to the said air inlet pipe and said venturi tube.

4. An air compressor as claimed in claim 2 wherein the intake pipe comprises a plurality of spaced housing tubes, an upper manifold and a lower manifold to which the said housing tubes are connected, each housing tube being provided with a flared discharge nozzle and a venturi tube, and an air inlet having a unidirectional valve.

5. An air compressor as claimed in claim 4 wherein a tube connects the lower manifold to the upper region of the pressure tank and an automatic cut-out valve in said tube which is operative to open at a predetermined air pressure in the pressure tank.

References Cited in the file of this patent UNITED STATES PATENTS 900,814 Wilson Oct. 13, 1908 

